Vacuum suction head

ABSTRACT

An etchable plate-shaped material is used as a vacuum suction pad  31.  On one surface thereof, a large number of independent protruded portions and recessed portions are formed to provide a suction part  33   b.  Further, a periphery of the suction part is annularly formed to provide an airtight part  33   a.  When the vacuum suction pad  31  comes close to a substrate to be sucked, a skirt pad  32  with a slit  32   d  is integrally formed in the shape of a hemmed hat using an elastic member, in order to block outside air into a peripheral space of the vacuum suction pad  31.  With this arrangement, it is possible to prevent the substrate from being locally deformed when the substrate is sucked by discharging air from a suction port  36  and to widen a clearance between the vacuum suction pad and the substrate such as a liquid crystal panel, at which the suction is possible.

TECHNICAL FIELD

The present invention relates to a vacuum suction head for holding andsucking a substrate when conveyed. The substrate herein means asingle-plate semiconductor wafer, a ceramic substrate, a glasssubstrate, a plastic substrate, a transmissive-type projector substratewhich is a laminated substrate, PDP (plasma display) which is a flatpanel display, a reflective-type liquid crystal projector substrate, aliquid crystal panel, an organic EL element substrate, and the like.Herein, a glass substrate and the like having a small thickness arecalled brittle material substrates. In the following, description willbe given using the liquid crystal panel as an example.

BACKGROUND ART

A conveyor robot or the like is used for supplying and removing amaterial to and from a substrate processing device and the like. FIG. 1shows a vacuum suction pad 1 of a first conventional example forconveying a substrate for use in a vacuum suction device of the conveyorrobot, and a liquid crystal panel 2, which is a laminated substrateformed by bonding substrates to be sucked together. As is well known,the liquid crystal panel 2 is formed in such a manner that, after twoglass substrates 3 a and 3 b are superposed with particulate spacers 4interposed therebetween, peripheral edges of the glass substrates 3 aand 3 b are fixed by using an adhesive (sealant) 5, followed byinjection of liquid crystal through a pore provided in a layer of theadhesive (sealant) 5. The vacuum suction pad 1 includes a rubber suctiondisk 1 a formed like an upside down bowl and a suction tube 1 b providedin a penetrating position through the top of the suction disk 1 a.

FIG. 2 shows a state where a lower edge peripheral portion 1 c of thesuction disk la is brought into press-contact with an upper surface ofthe liquid crystal panel 2 to perform vacuum suction through the suctiontube 1 b. By this vacuum suction, a vacuum-sucked place of the upperglass substrate 3 a might be locally deformed upward to cause anincrease in a gap between the upper and lower glass substrates in thisplace, thereby temporally lowering pressure. In this case, the liquidcrystal flows, as if concentrated, into this place. The spacers 4 with adiameter of, for example, 5 to 10 μm are inserted so as to have auniform density of about 100 particles/mm². However, being unfixed tothe glass substrates 3 a and 3 b, the spacers 4 move along with themovement of the liquid crystal. When no liquid crystal has been injectedinto the liquid crystal panel 2, air flow into a place where pressurehas been lowered. In this case, because the resistance to the movementof the spacers 4 is small, the movement of the spacers 4 is furthercontributed.

Consequently, after the suction by the vacuum suction pad 1, dispersionin the distribution of the spacers 4 has occurred, and corresponding tothis dispersion, variations in the gap between the upper and lower glasssubstrates have occurred, as shown in FIG. 3. Further, although notshown in the figure, there recently exists a liquid crystal panel of thetype obtained by bonding two glass substrates together without spacers,and this spacer-free type liquid crystal panel is configured in a statewhere the spacers 4 are not inserted into the liquid crystal panel 2 inFIGS. 1 to 3. Also in the case this spacer-free type liquid crystalpanel is vacuum-sucked by the suction disk 1 a, the upper glasssubstrate 3 a is locally deformed upward, and once deformed, it does notchanged back into the original form, thereby causing variations in thegap between the upper and lower glass substrates. If the gap between theupper and lower glass substrates of the liquid crystal panel varies by0.04 mm or more, a color shading appears on the display surface, withwhich the liquid crystal panel becomes defective as a product.

As thus described, in the first conventional example, the deformation ofthe upper glass substrate occurs when the vacuum suction pad 1vacuum-sucks the liquid crystal panel 2, caused by too large a diameterof the suction disk 1 a as compared to the thickness of the glasssubstrate and the size of the spacer 4. The diameter of the suction disk1 a is several tens of mm while the thickness of the glass substrate is0.5 to 1.1 mm, and a thin glass substrate tends to be selected.

In the vacuum suction pad 1 of FIG. 1, suction force becomesinsufficient if the size of the suction disk 1 a is reduced for thepurpose of avoiding the problems of the local deformation of the suctionsurface of the glass substrate, the variations in the gap between theglass substrates due to the suction by the vacuum suction pad 1 and theproblem of the dispersion in the distribution, which results from thelocal deformation and the variations in the gap, of the spacers 4. Tothis end, as shown in FIG. 4, there is a method for providing aplurality of vacuum suction pads 1 each having a small suction disk tosuck the liquid crystal panel 2. In this case, it is necessary to attachall the vacuum suction pads 1 to the vacuum suction device such that thesuction surface of each of the vacuum suction pads 1 is provided withina prescribed attachment tolerance range in order to prevent the vacuumsuction pads 1 from pressing the glass substrate surface. Further, alsoin the case the liquid crystal panel 2 to be sucked is swollen or bent,it is necessary to set the suction surface of each of the vacuum suctionpads 1 within a clearance at which the suction of the liquid crystalpanel 2 is possible.

If the plurality of vacuum suction pads 1 are attached to the vacuumsuction device with the suction surfaces thereof out of theabove-mentioned attachment tolerance range, the liquid crystal panel 2is conveyed while imperfectly sucked, whereby the liquid crystal panel 2might drop when conveyed, or might be pressed by the vacuum suction pad1 when sucked to cause occurrence of variations in the gap between theupper and lower glass substrates, leading to occurrence of productdefect.

FIG. 5 is an exploded view showing a structure of a vacuum suction pad21 in a second conventional example, shown in JP-A 11-019838. A suctiondisk 22 of the vacuum suction pad 21 is formed into a disk shape and ismade of a photosensitive resin material, a central portion of which isprovided with a vertically penetrating suction port 22 c, and a suctionsurface of the suction disk 22 is provided with a large number ofprotruded portions and recessed portions, as described later. Theselarge number of protruded portions and recessed portions are formed byetching the photosensitive resin material.

FIG. 6 shows the structure of the suction surface of the suction disk 22in the vacuum suction pad 21, and FIG. 7 shows a cross-sectional view ofthe vacuum suction pad 21. The suction disk 22 has an airtight part 22 aat a peripheral portion thereof with a flat surface, and a suction part22 b where a large number of protruded portions and recessed portionsare formed. As shown in FIG. 7, a reinforcement layer 23 is a layer madeof a large rigid plate material so as to prevent the photosensitiveresin material from being deformed due to an external stress, and isbonded to the photosensitive resin material in the stage ofmanufacturing the photosensitive resin material into a plate-makingmaterial. A magnet sheet 24 is a sheet with the same diameter as that ofthe suction disk 22. A double-faced adhesive sheet 25 is an adhesivesheet for joining the magnet sheet 24 and the reinforcement sheet 23together, and has the same diameter as that of the suction part 22 b onthe suction disk 22. A hole Q is formed in a position corresponding tothe suction port 22 c, in each of those members 23 to 25.

In the case of making the diameter of the double-faced adhesive sheet 25equivalent to the diameter of the suction part 22 b, as shown in FIG. 7,only the suction part 22 b on the suction disk 22 is fixed to asupporting member 26 via the magnet sheet 24. Meanwhile, the airtightpart 22 a is not fixed and stays free. FIG. 8 shows an example where thediameter of the double-faced adhesive sheet 25 is made equivalent tothat of the suction disk 22, and in this case, the whole surface of thesuction disk 22 is fixed to the supporting member 26.

Turning back to FIG. 6, an expanded view X of the peripheral portion ofthe suction disk 22 is referred to. The airtight part 22 a is a regionwhere the photosensitive resin material is not etched. In the suctionpart 22 b, a large number of small-circular regions are non-etchingportions (protruded portions) and the regions other than the protrudedportions are etching portions (recessed portions). As shown in theexpanded view X in FIG. 6, the small circular places are left asprotruded portions M and the other places become recessed portions N.Herein, the protruded portions M and the airtight part 22 a are bothnon-etching portions and thus positioned on the same surface.

The supporting member 26 is an iron material having the same diameter asthat of the magnet sheet 24, and a supporting part 26 a is integrallyformed at a central portion corresponding to the suction port 22 c ofthe suction disk 22. A suction tube 27 is inserted through thesupporting part 26 a and is connected to a vacuum pump (not shown). Thesuction disk 22 is integrally joined with the reinforcement layer 23,the double-faced adhesive sheet 25 and the magnet sheet 24, and is madeattachable to/detachable from the supporting member 26 by the action ofthe magnet sheet 24.

When the vacuum suction pad 21 as thus configured is brought intopress-contact with the flat liquid crystal panel 2, the recessedportions N in the suction part 22 b on the suction disk 22 form closedspaces with the airtight part 22 a, and since the protruded portions Mare independent of one another, the suction port 22 c of the suctiondisk 22 is communicated with the closed spaces as shown in FIG. 5,whereby the vacuum suction is performed using the foregoing vacuum pump(not shown) through the suction port 22 c, allowing the suction disk 22to be sucked to the liquid crystal panel 2.

FIG. 9 is a cross-sectional view showing a state of sucking a liquidcrystal panel 2 having a small outer shape with the use of the foregoingvacuum suction pad 21 of the second conventional example. In this case,in order to hold the substrate, one vacuum suction pad 21 is used forthe vacuum suction device to be installed in a conveyor robot or thelike, and the size of the liquid crystal panel 2 is in such a degree asto be slightly larger than that of the vacuum suction pad 21. When theliquid crystal panel 2 is made to be sucked by the vacuum suction pad21, the large number of protruded portions M formed on the same surfaceas the airtight part 22 a in the expanded view X of FIG. 6 are broughtinto contact with the upper surface of the upper glass substrate 3 a inthe liquid crystal panel 2, which can prevent local deformation of theupper glass substrate 3 a in the liquid crystal panel 2, and hencevariations in the gap between the upper glass substrate 3 a and thelower glass substrate 3 b does not occur. Moreover, also in the case ofthe liquid crystal panel of which the gap is formed without insertion ofthe spacers, no variations in the gap between the upper and lower glasssubstrates occur. It should be noted that, in the case the suction disk22 itself is sufficiently flexible, the vacuum suction pad 21 may be avacuum suction pad of the type obtained by fixing the whole surface ofthe suction disk 22 with the double-faced adhesive sheet 25, as shown inFIG. 8.

In the case the liquid crystal panel for use in individual displaydevices has a small shape, a mother liquid crystal panel is segmented tomanufacture a plurality of liquid crystal panels of a prescribed size.An example of such a panel is a liquid crystal panel to be used formobile phones, personal digital assistances (PDAs) and the like. On theother hand, in the case of a liquid crystal panel having a large outershape, a plurality of vacuum suction pads are used as in the vacuumsuction devices shown in FIG. 4.

In the case one vacuum suction device is provided with a plurality ofvacuum suction pads, when the vacuum suction pad 1 of the firstconventional example is used as shown in FIG. 4, as described above, inthe liquid crystal panel, the local deformation of the upper glasssubstrate occurs and dispersion in the distribution of the foregoingspacers occurs caused by the local deformation, to bring aboutoccurrence of product defect. For this reason, the vacuum suction pad 21of the second conventional example is used.

There exists a distance (clearance) at which the vacuum suction pad cansuck the liquid crystal panel. In the vacuum suction pad 21 having thestructure shown in FIG. 5, air is discharged through the suction tube27. At this time, the vacuum suction pad 21 sucks the air in frontthereof so as to suck the liquid crystal panel. A distance from thesurface of the upper glass substrate in the liquid crystal panel to thesuction disk 22 of the vacuum suction pad 21 at this time is referred toas a clearance at which the suction is possible. The conventionalclearance is 0.0 to 0.3 mm, and since the adequate range is very narrow,it has been very difficult to maintain the clearance and also to adjustthe same.

As shown in FIGS. 10(a) and (b), with the liquid crystal panel 2 swollenor bent, even if a plurality of vacuum suction pads 21 are provided inthe vacuum suction device within a prescribed attachment tolerancerange, there have been cases where the clearance G between the uppersurface of the liquid crystal panel 2 and the vacuum suction pad 21exceed the clearance at which the suction of the vacuum suction pad 21is possible. In such a case, any one of the plurality of vacuum suctionpads 21 cannot suck the liquid crystal panel 2 in a regular state, andthe liquid crystal panel 2 is conveyed while imperfectly sucked, whichmight result in that the liquid crystal panel 2 drops when conveyed, orsince the vacuum suction pad 21 presses the liquid crystal panel 2 insucking the liquid crystal panel 2, the upper glass substrate in theliquid crystal panel 2 is locally deformed to lead to occurrence ofvariations in the gap between the upper and lower glass substrates.

The present invention has been made to solve the above-mentionedproblems, and an object thereof is to provide a vacuum suction head,comprising a vacuum suction pad which can hold a substrate being swollenor bent without making the substrate defective, widen a clearancebetween the vacuum suction pad and the substrate at which the suction ispossible during the suction, and prevent local deformation of thesubstrate due to the suction as well as preventing occurrence ofvariations in the gap between the upper and lower glass substratescaused by the local deformation in the case of the laminated substratesuch as a liquid crystal panel.

DISCLOSURE OF INVENTION

The present invention provides a vacuum suction head for vacuum-suckinga substrate, comprising: a vacuum suction pad which is made of aplate-shaped material and is provided with a suction part where a largenumber of independent protruded portions and recessed portions areformed on one surface thereof, an airtight part annularly formed in aperipheral position of the plate-shaped material surrounding the suctionpart, a groove part serving as a passage for discharging air from thesuction part, and an opening for discharging the air from the groovepart to the outside; and an elastic member which is formed so as to takein the vacuum suction pad, and blocks outside air from a peripheralspace of the vacuum suction pad when the vacuum suction pad comes closeto a substrate to be sucked, wherein the elastic member also has afunction of leaking air from the outside of the elastic member into theinside thereof.

Herein, the elastic member may be a skirt pad formed into a skirt shape,and include: a plate part which supports the vacuum suction pad frombehind a suction surface; an annular part which is formed into a thickannular shape on an outer edge of the plate part so as to surround aperipheral portion of the vacuum suction pad via a prescribed gap; and askirt part which is formed into a conically annular shape by making athickness of the skirt part smaller than that of a peripheral portion ofthe annular part.

This skirt pad may communicate the outside of the annular part with theinside space, and provide a slit in the annular part, for leaking airfrom the outside into the inside space when there is a large adifference in pressure between the outside and the inside space.

Further, the elastic member may be a cylindrically formed sponge pad,and the elastic member may be formed into a cylindrical shape using anopen foam sponge member so as to block a peripheral space of the vacuumsuction pad from outside air when the vacuum suction pad comes close tothe substrate to be sucked, and leak air from the outside into theinside when there is a difference in pressure between the outside andthe inside space in the blocked state.

The suction part of the vacuum suction pad may be formed on one surfaceof an etchable plate-shaped member by forming a large number ofindependent protruded portions and recessed portions by etching, and theairtight part may be annularly formed on the peripheral portion of theplate-shaped member as a non-etching region.

The vacuum suction pad may be made of a photosensitive resin materialwhich can be selectively etched with the use of ultraviolet irradiationand a solvent.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view showing a positional relation between avacuum suction pad of a first conventional example and a liquid crystalpanel which is a brittle material substrate to be sucked.

FIG. 2 is a cross-sectional view showing a state where a lower edgeperipheral portion of a suction disk is brought into press-contact withan upper surface of the liquid crystal panel to perform vacuum suctionthrough a suction tube in the vacuum suction pad of the firstconventional example.

FIG. 3 is an explanatory view showing a state where dispersion in thedistribution of spacers has occurred after suction and variations in thegap between glass substrates has also occurred according to thedispersion in the distribution in the case of using the vacuum suctionpad of the first conventional example.

FIG. 4 is an external view showing a configuration of a vacuum suctiondevice of a conventional example provided with a plurality of vacuumsuction pads.

FIG. 5 is an exploded perspective view showing a structure of a vacuumsuction pad in a second conventional example.

FIG. 6 is a plan view of a suction disk of the vacuum suction pad of thesecond conventional example as seen from the below.

FIG. 7 is a cross-sectional view showing the structure of the suctiondisk in the vacuum suction pad of the second conventional example.

FIG. 8 is a cross-sectional view showing the case where a diameter of adouble-faced adhesive sheet is made equivalent to the diameter of thesuction disk in the vacuum suction pad of the second conventionalexample.

FIG. 9 is a cross-sectional view showing a state where a liquid crystalpanel having a small outer shape is sucked using the vacuum suction padof the second conventional example.

FIGS. 10(a) and 10(b) are explanatory views each showing a clearancebetween the vacuum suction pad and a liquid crystal panel with a bentportion in the second conventional example.

FIG. 11 is an end view showing a structure of a vacuum suction head inEmbodiment 1 of the present invention.

FIG. 12 is a plan view of the structure of the suction surface of thevacuum suction head in Embodiment 1 of the present invention.

FIG. 13 is a cross-sectional view showing a state of sucking the liquidcrystal panel when a slit-free vacuum suction head is used.

FIG. 14 is a cross-sectional view showing a transitional state ofsucking the liquid crystal panel when the vacuum suction head inEmbodiment 1 of the present invention is used.

FIG. 15 is a cross-sectional view showing a state of sucking the liquidcrystal panel when the vacuum suction head in Embodiment 1 of thepresent invention is used.

FIG. 16 is an end view showing a structure of a vacuum suction head inEmbodiment 2 of the present invention.

FIG. 17 is a cross-sectional view showing a transitional state ofsucking the liquid crystal panel when the vacuum suction head inEmbodiment 2 is used.

FIG. 18 is a cross-sectional view showing a state of sucking the liquidcrystal panel when the vacuum suction head in Embodiment 2 is used.

FIG. 19 is a plan view showing a structure of another suction disk foruse in a vacuum suction head in each embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

A vacuum suction head in Embodiment 1 of the present invention will bedescribed with reference to the drawings. A substrate herein means asingle-plate semiconductor wafer, a ceramic substrate, a glasssubstrate, a plastic substrate, a transmissive-type projector substratewhich is a laminated substrate, PDP (plasma display) which is a flatpanel display, a reflective-type liquid projector substrate, a liquidcrystal panel, an organic EL element substrate and the like. While thevacuum suction head of the present invention is effectively applicableto a liquid crystal panel and a mother liquid crystal panel with nospacer inserted therein, an example of a liquid crystal panel withspacers inserted therein will be described herein. FIG. 11 is an endview showing a structure of a vacuum suction head 30A in Embodiment 1.The vacuum suction head 30A includes a vacuum suction pad 31 and a skirtpad 32. FIG. 12 is a plan view showing a structure of a suction surface(suction disk 33) of the vacuum suction pad 31.

The vacuum suction pad 31 has a similar structure to the structure ofthe vacuum suction pad shown in FIGS. 6 and 7, which is a multilayerstructure where a suction disk 33 and a reinforcement layer 34 arejoined with a double-faced adhesive sheet 35 a. The suction disk 33 hasan airtight part 33 a on a peripheral flat surface and a suction part 33b where a larger number of protruded portions and recessed portions areformed.

The suction disk 33 is formed into a disk shape and is made of aphotosensitive resin material, a central portion of which is providedwith an opening 33 d as part of a vertically penetrating suction port36. The large number of protruded portions and recessed portions in thesuction part 33 b are formed by etching the photosensitive resinmaterial. As the photosensitive resin material, AFP as a printing platematerial is used, for example. In this AFP, protruded portions andrecessed portions can be selectively formed with the use of ultravioletirradiation and a solvent. It should be noted that the material for thesuction disk 33 is not restricted to the printing plate material so longas being a photosensitive resin material. Metal plates, ceramic and thelike can also be etched, and if a similar processing method to thisetching is applicable, such a method may be employed.

In the case of using the photosensitive resin material, a film with adesired pattern printed thereon is bonded as a mask to the surface of asheet-shaped photosensitive resin plate. The bonded film is irradiatedwith (exposed to) ultraviolet rays, and thereafter, the photosensitiveresin is etched (developed) with a treatment liquid. In such a manner,places other than the patterned places are etched to form recessedportions whereas the patterned places through which no light istransmitted are not etched to be left as protruded portions.

The distribution density of the protruded portions is from 10 to 250mesh/inch², and the sizes of the individual protruding portions are setsuch that the area ratio of the whole protruded portions to the suctionpart 33 b is from 10 to 50%. Further, the depth of the recessed portion(etched depth) is sufficiently large when it is from tens of μm tohundreds of μm. It should be noted that the shape of the protrudedportions is not restricted to a circle, and an arbitrary shape, such asa polygon, may also be applied.

The airtight part 33 a is a region of the photosensitive resin materialwhich is not etched. Herein, since neither the protruded portions northe airtight part 33 a are etched, they are positioned on the samesurface. Further, the inner circumferential side of the airtight part 33a is provided with an annular groove 33 c as another recessed portion.Moreover, the center of the suction disk 33 is provided with the opening33 d, through which a cross-shaped groove 33 e is formed. These groovesare communicated with the opening 33 d and serve as passages when airpresent in the recessed portions is discharged.

The reinforcement layer 34 is a layer bonded to the suction disk 33 soas to prevent deformation of the photosensitive resin materialconstituting the suction disk 33 due to an external stress. This layeris bonded via a double-faced adhesive sheet 35 a in the stage ofmanufacturing the photosensitive resin material into a plate-makingmaterial. The central portion of the reinforcement layer 34 is alsoprovided with an opening.

The skirt pad 32 is an elastic member newly provided in the presentinvention, which is rubber obtained by integral formation of a platepart 32 a, an annular part 32 b and a skirt part 32 c. The plate part 32a is a disk-shaped holding member for holding the vacuum suction pad 31via a double-faced adhesive sheet 35 b, and the diameter thereof issufficiently larger than the outer diameter of the vacuum suction pad31. The center of the plate part 32 a is also provided with an opening,which is communicated with the opening of the vacuum suction pad 31 toform the suction port 36. The annular part 32 b is formed thick andannularly on the outer edge of the plate part 32 a so as to surround thevacuum suction pad 31 at a prescribed spacing, and the lower surface ofthe annular part 32 b is formed in a position higher than the lowersurface of the vacuum suction pad 31 such that the vacuum suction pad 31protrudes downward from the annular part 32 b. The skirt part 32 c is athin annular rubber member conically expanded, with the annular part 32b as the root, in the direction facing the substrate. An example of thisrubber member includes nitrile rubber.

The skirt pad 32 serves to widen the air-discharging space on theperiphery of the suction part when sucking the substrate, so as to widenthe clearance between the vacuum suction pad 31 and the substrate atwhich the suction is possible. Since the skirt part 32 c is thin, whenthe vacuum suction head 30A is brought close to the substrate, theperipheral portion of the vacuum suction head 30A is brought intocontact with the substrate to be elastically deformed. As thusdescribed, the skirt part 32 c of the skirt pad 32 exerts a sealingfunction of blocking the air flowing in from the outside by the contactwith the substrate.

A slit 32 d is a cut provided in the annular part 32 b so as to leak theair between the outside and the inside of the skirt. This slit 32 d canbe realized by making a cut with the use of a thin blade in part of theside surface of the skirt pad 32 after formation.

It is to be noted that the slit 32 d is not restricted to this formationmethod and shape. The slit 32 d may be a through hole small enough tohold the inside space in a negative pressure state after the skirt pad32 comes into contact with the glass substrate till the vacuum suctionpad 31 comes into contact with the substrate, and not to interfere withthe suction of the substrate by the vacuum suction pad 31, and may forexample be a round hole with a microdiameter.

Further, the lower surface of the annular part 32 b is positioned higherthan the lower surface of the vacuum suction pad 31 such that the vacuumsuction pad 31 protrudes downward from the annular part 32 b. Hence theannular part 32 b does not come into contact with the liquid crystalpanel 2 even when the vacuum suction pad 31 comes into contact with theliquid crystal panel 2. This can prevent deformation of the annular part32 b to close the slit 32 d.

Herein, the function of the slit 32 d will be further described. Avacuum suction head of the type without the slit 32 d is referred to asa vacuum suction head 30B. FIG. 13 is a cross-sectional view showing astate where the vacuum suction head 30B sucks the liquid crystal panel2. As described above, the liquid crystal panel 2 is in a state where aconstant gap is held between the upper glass substrate 3 a and the lowerglass substrate 3 b via spacers S. When the vacuum suction head 30B isbrought close to the liquid crystal panel 2 and air is discharged fromthe suction port 36, as shown in the figure, the skirt part 32 c adheresto the liquid crystal panel 2 and the space covered with the skirt part32 c is held in a negative pressure state. In course of time, thesuction disk 33 also adheres to the liquid crystal panel 2 and the airis further discharged to act suction force upon the liquid crystal panel2.

A space V1 generates since the vacuum suction pad 31 is positioned lowerthan the lower end of the annular part 32 b and the lower surface of theannular part 32 b as the root of the skirt part 32 c is positionedhigher than the lower surface of the vacuum suction pad 31. The space V1is formed of a spacing between the vacuum suction pad 31 and the annularpart 32 b, and the space V1 becomes even wider when the differencebetween the outer diameter of the vacuum suction pad 31 and the innerdiameter of the annular part 32 b is large. As described in theconventional example, the glass substrates 3 a and 3 b have a thicknessas thin as 0.5 to 1.1 mm, and when the negative pressure is actedthereon, the upper glass substrate 3 a is locally deformed upward inportions x1 and x2, as shown in FIG. 13. In such a state, the gapbetween the upper glass substrate 3 a and the lower glass substrate 3 bwidens, and the spacers S then move to the portions x1 and x2 where thegap has widened. Moreover, there exists a liquid crystal panel of FIG.13 of the type with no spacer S inserted between the upper and lowerglass substrates in the liquid crystal panel 2. Also in the case thisspacer-free type liquid crystal panel is vacuum-sucked by a suction head30B, the upper glass substrate 3 a is locally deformed upward and oncedeformed, it does not returns to the original state, to cause occurrenceof variations in the gap between the upper and lower glass substrates,thereby leading to appearance of a color shading on the display surface,and hence the liquid crystal panel becomes defective as a product.

In order to solve this problem, as shown in FIG. 11, the skirt pad 32 isprovided with the slit 32 d for air-inspiration. The vacuum suction pad31 is provided so as to protrude downward from the annular part 32 bsuch that the annular part 32 b is prevented from being deformed toclose the slit 32 d even with the vacuum suction pad 31 brought intocontact with the liquid crystal panel 2. Therefore the lower surface ofthe annular part 32 b is positioned higher than the lower surface of thevacuum suction pad 31. FIG. 14 shows a transitional state of sucking theliquid crystal panel by the vacuum suction head 30A, and FIG. 15 shows asteady sucking state.

When the air is discharged through the suction port 36 to suck theliquid crystal panel 2, as shown in FIG. 14, first, the skirt part 32 cis brought into contact with the liquid crystal panel 2. When the aircontinues to be discharged in this state, the pressure in the spacecovered with the skirt part 32 c and the upper glass substrate 3 abecomes negative. This causes elastic deformation of the skirt part 32 cto increase a contact area between the skirt part 32 c and the upperglass substrate 3 a. Further, since the negative pressure inside theskirt part 32 c becomes larger, the air begins to be leaked from theoutside through the slit 32 d.

Although this causes decreased negative pressure on the periphery of thesuction disk 33, the negative pressure in such a degree does not preventthe vacuum suction pad 31 from sucking the liquid crystal panel 2, andthe liquid crystal panel 2 is thus sucked by the vacuum suction pad 31.When the air-discharging further continues, as shown in FIG. 15, thesuction disk 33 of the vacuum suction pad 31 is brought into contactwith the liquid crystal panel 2. In such a state, the negative pressureupon the upper glass substrate 3 a of the suction disk 33 furtherincreases due to the sealing function of the airtight part 33 a. Thesuction disk 33 thus comes into a state of being capable of singlysucking and holding the liquid crystal panel 2. Thereafter, the outsideair is further leaked through the slit 32 d into the space V1, toeliminate the negative pressure. When the suction is performed in such amanner, the pressure in the space V1 is kept almost equivalent to theoutside pressure, and the upper glass substrate 3 a is not locallydeformed as in FIG. 13. Therefore, the spacers S do not move and it isthus possible to suck and hold the liquid crystal panel 2 while holdingthe gap between the glass substrates in a uniform state.

In the case a brittle material substrate having a large outer shape issucked using a plurality of vacuum suction heads 30A with the structurethus described, the distance at which suction is possible becomes longerthan that in the conventional example, and in one example, the distancewas from 0.0 to 2.0 mm. Therefore, even with the brittle materialsubstrate swollen or bent in some degree, it was possible for thesuction disk 33 to follow so as to hold the substrate with certainty.

Embodiment 2

Next, a vacuum suction head in Embodiment 2 of the present inventionwill be described with reference to the drawings. FIG. 16 is an end viewshowing a structure of a vacuum suction head 40 in Embodiment 2. Thevacuum suction head 40 includes the vacuum suction pad 31, a plate part41 and a sponge pad 42. The vacuum suction pad 31 and the sponge pad 42are concentrically attached to the plate part 41.

Since the structure of the vacuum suction pad 41 is the same as thatshown in FIGS. 11 and 12, descriptions on the constituents thereof areomitted. The sponge pad 42 is an elastic member having the same functionas the skirt pad 32 shown in FIG. 11. The sponge pad 42 is made ofporous rubber and is cylindrically formed. As the porous rubber,especially one with large loss of pressure is used. Used herein is asponge body of EPT (Ethylene Propylene Terpolymer) which is excellent inweather resistance, heat resistance and aging resistance. As the spongebody, an open-cell foamed type with a desired pressure loss ispreferably used. When a center axis of the vacuum suction pad 31 is z,the height of the sponge pad 42 in the z direction in a non-deformedstate is slightly larger than the thickness of the vacuum suction pad 31in the z direction. The center axis of the vacuum suction pad 31 isprovided with a suction port 43.

FIG. 17 shows a transitional state of sucking the liquid crystal panel 2by the vacuum suction head 40, and FIG. 18 shows a steady sucking state.When the vacuum suction head 40 is brought close to the liquid crystalpanel 2, as shown in FIG. 17, first, the lower end of the sponge pad 42is brought into contact with the upper glass substrate 3 a , and thesponge pad 42 is bent due to the elasticity thereof in such a directionas to increase the thickness thereof. When the air is discharged fromthe suction port 43, pressure of a closed space covered with the spongepad 42 becomes negative, and due to the difference between the outsidepressure and the inside pressure of the sponge pad 42, the air flowsinto the closed space from the outside as indicated by arrows in FIG.17. However, the flowing of the air inside does not cause a decrease innegative pressure of the closed space in such a degree as to prevent thevacuum suction pad 31 from sucking the liquid crystal panel 2. In thismanner, the liquid crystal panel 2 is further sucked by the vacuumsuction pad 31, and as shown in FIG. 18, the suction disk 33 of thevacuum suction pad 31 is brought into contact with the liquid crystalpanel 2. At this time, due to the sealing function of the airtight part33 a, the suction disk 33 has negative pressure upon the upper glasssubstrate 3 a large enough to singly suck and hold the liquid crystalpanel 2. On the other hand, the outside air is flown into a space V2between the sponge pad 42 and the vacuum suction pad 31 due to thedifference between the outside pressure and the inside pressure of thesponge pad 42, and thereby the negative pressure of the space V2 isinstantly eliminated. Therefore, the upper glass substrate 3 a in thisportion is no longer locally deformed upward. Accordingly, the spacers Sdo not move, and it is thus possible to suck and hold the liquid crystalpanel 2 with certainty while holding the gap between the glasssubstrates in a uniform state.

In the case a brittle material substrate having a large outer shape issucked using a plurality of vacuum suction heads 40 with the structurethus described, the distance at which the suction is possible becomeslonger than that in the conventional example. In one example, thedistance was from 0.0 to 2.0 mm, and even with the brittle materialsubstrate swollen or bent in some degree, it has become possible for thesuction disk 33 to follow so as to hold the brittle material substratewith certainty.

It should be noted that, as the vacuum suction pad in Embodiments 1 and2, minute protruded portions were left and recessed portionscommunicated with one another by etching were formed in the suctionpart, as shown in FIG. 12. However, as shown in FIG. 19, a large numberof grooves may be formed and portions surrounded with the grooves may bethe protruded portions, in place of forming minute protruded portions.In a suction disk 50 shown in FIG. 19, the peripheral portion is anairtight part 50 a, and a plurality of grooves 50 c are concentricallyformed by etching with an opening 50 b at the center, and a groove 50 dis formed in cross shape by etching so as to cross over the opening 50b. The regions not etched are protruded portions 50 e. Also in thesuction disk 50 with such a structure, the same suction effect as thosein Embodiments 1 and 2 is obtained and the distance at which the suctionis possible is also increased.

It should be noted that, although the liquid crystal panel was mainlyused as the substrate in the descriptions on Embodiments 1 and 2, thevacuum suction head of the present invention is effectively applicableto a single-plate semiconductor wafer, a ceramic substrate, a glasssubstrate, a plastic substrate, a transmissive-type projector substratewhich is a laminated substrate, a reflective-type liquid projectorsubstrate, a plasma display panel (PDP) which is a flat panel display, aliquid crystal panel, an organic EL element substrate, and the like,since the vacuum suction head can suck these substrates without causinglocal deformation thereof. Further, although the case where spacers areinserted between the two glass substrates in the liquid crystal paneland the mother liquid crystal panel was described, the vacuum suctionhead of the present invention is effectively applicable also to a liquidcrystal panel and a mother liquid crystal panel with no spacer insertedtherein.

Industrial Applicability

According to the present invention, since the elastic member is providedwith the peripheral portion of the suction disk, it is possible topromptly and stably make the pressure negative on the periphery of thesuction disk immediately before the suction of the substrate.Subsequently, as the suction disk adheres to the substrate, thesubstrate is held such that the suction force of the suction disk on thesubstrate further increases. In such a manner, a clearance at which thesubstrate can be sucked by the suction disk (i.e. clearance between thesubstrate and the suction surface of the suction disk) widens, therebypreventing occurrence of defective suction when a substrate having alarge shape is sucked using a plurality of suction disks. Moreover, itis possible to prevent local deformation of the substrate that occurs atthe time of sucking the substrate, and in the case of a laminatedsubstrate, it is possible to prevent variations in the gap between thesubstrates caused by the above-mentioned local deformation of thesubstrate. Furthermore, since the elastic member absorbs the localdeformation of the substrate that occurs at the time of suction to allowthe substrate to adhere to the suction disk with stable suction force,stable suction is possible when a large substrate is sucked using aplurality of suction disks. Such a vacuum suction head is preferablyapplicable to a substrate scribing device and a substrate conveyingdevice.

1. A vacuum suction head for vacuum-sucking a substrate, comprising: avacuum suction pad which is made of a plate-shaped material and isprovided with a suction part where a large number of independentprotruded portions and recessed portions are formed on one surfacethereof, an airtight part annularly formed in a peripheral position ofsaid plate-shaped material surrounding said suction part, a groove partserving as a passage for discharging air from said suction part, and anopening for discharging the air from said groove part to the outside;and an elastic member which is formed so as to take in said vacuumsuction pad, and blocks outside air from a peripheral space of saidvacuum suction pad when said vacuum suction pad comes close to asubstrate to be sucked, wherein said elastic member also has a functionof leaking air from the outside of the elastic member into the insidethereof.
 2. The vacuum suction head according to claim 1, wherein saidelastic member is a skirt pad formed into a skirt shape, and comprises:a plate part which supports said vacuum suction pad from behind asuction surface; an annular part which is formed into a thick annularshape on an outer edge of said plate part so as to surround a peripheralportion of said vacuum suction pad via a prescribed gap; and a skirtpart which is formed into a conically annular shape by making athickness of the skirt part smaller than that of a peripheral portion ofsaid annular part.
 3. The vacuum suction head according to claim 2,wherein said skirt pad communicates the outside of said annular partwith the inside space, and provides a slit in said annular part, forleaking air from said outside into the inside space when there is alarge a difference in pressure between said outside and the insidespace.
 4. The vacuum suction head according to claim 1, wherein saidelastic member is a cylindrically formed sponge pad, and said elasticmember is formed into a cylindrical shape using an open foam spongemember so as to block a peripheral space of said vacuum suction pad fromoutside air when said vacuum suction pad comes close to the substrate tobe sucked, and leaks air from said outside into the inside when there isa difference in pressure between the outside and the inside space in theblocked state.
 5. The vacuum suction head according to claim 1, whereinthe suction part of said vacuum suction pad is formed on one surface ofan etchable plate-shaped member by forming a large number of independentprotruded portions and recessed portions by etching, and said airtightpart is annularly formed on the peripheral portion of said plate-shapedmember as a non-etching region.
 6. The vacuum suction head according toclaim 5, wherein said vacuum suction pad is made of a photosensitiveresin material which can be selectively etched with the use ofultraviolet irradiation and a solvent.